A group of 75 former players have filed suit against the league, claiming it intentionally kept players in the dark about the seriousness of concussions for the past 90 years. In recent years, the NFL has made a concerted effort to more proactively prevent concussions, and striven to keep concussed players off the gridiron, but this is too little, too late for a field full of former players still feeling the effects of concussions sustained during their careers.

According to an ESPN article, the plaintiffs claim the NFL “knew as early as the 1920s of the harmful effects on a player's brain of concussions; however, until June of 2010 they concealed these facts from coaches, trainers, players and the public.” The league, however, released a statement Tuesday saying that it has not yet seen the players’ complaint, but would vigorously contest any claims of this kind.

Also named as a defendant is helmet-maker Riddell, which also released a statement saying that it has not yet reviewed the complaint and refused to comment on any pending litigation.

The players assert the NFL authorized a study in 1994 that concluded there was “no evidence of worsening injury or chronic cumulative effects” from multiple concussions, the ESPN article states. The players go on to note that the league only warned active players in June 2010 about the risks that come with multiple concussions, and that Riddell also neglected to caution the players of concussion dangers until around that same time.